The time we spend asleep is meant to be the most relaxing and restorative period of our days. Yet for those who suffer from sleep apnea, nighttime can become a struggle to breathe; a true nightmare in which the body's need for rest is continuously interrupted by its even greater need to breathe.

Sleep apnea affects more than 100 million people worldwide [source: World Health Organization] and is thought to afflict millions more who remain undiagnosed. It is more common in men, those who are overweight, those with a history of the condition in their family and those who are of African American, Hispanic or Pacific Island descent [source: National Heart Lung and Blood Institute]. It is also more prevalent in people over 40 [source: FamilyDoctor].

There are two main types of sleep apnea, a term that takes its name from the Greek phrase for "want of breath." In obstructive sleep apnea, a portion of the airway actually closes while sleeping, causing a pause in breathing that can last for a few seconds to as long as two minutes. These breathing pauses can occur up to 30 times per hour.

With central sleep apnea, the brain fails to send the proper signals to the muscles that control breathing. This also causes repeated interruptions to the sleep cycle.

In both cases, the lack of solid sleep and a steady flow of oxygen can have serious consequences. The U.S. National Commission on Sleep Disorders has estimated that roughly 38,000 deaths per year occur from cardiovascular issues connected to sleep apnea, including hypertension, stroke and high blood pressure [source: Sleep Disorders Guide]. Sleep apnea has also been linked to an increased risk of type II diabetes. And the condition can put other people at risk, not only in the bedroom -- since the partners of people with sleep apnea often experience lost sleep as well -- sometimes even on the roadways. It is estimated that men and women who have sleep apnea issues are three to five times more likely to be involved in a serious car crash involving personal injury than people without the disease [source: University of British Columbia].

In addition to the excessive daytime sleepiness that can lead to these motor vehicle accidents, another key symptom of sleep apnea is restless sleep and/or excessive snoring. For this reason, sleep apnea is best spotted by a partner, who can notice the pauses in breathing followed by a gasp or grunt as the afflicted person struggles to resume breathing. Other symptoms include difficulty concentrating, morning headaches and/or a dry throat, shortness of breath that gets better when sitting up, and mood swings or irritability.

Fortunately, the cure for sleep apnea in most cases is relatively simple and pain free, as well see on the next page.

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